1. Field of Invention
The present invention relates to a computer switch. More particularly, the present invention relates to a keyboard-mouse-video switch with a digital visual interface.
2. Description of Related Art
With the rapid development in information technology, computers and their peripherals have become very popular. Typically, each computer is equipped with one set of manipulation and display devices, including a keyboard, a mouse, a monitor, and a speaker. However, this equipment wastes money and space if one has several computers. Therefore, a keyboard-video-mouse (KVM) switch is proposed to use at least one set of manipulation and display devices to manage several computers and their peripherals. Using the KVM switch reduces costs and decreases the waste of space while simultaneously conquering the problem of compatibility between different interfaces.
Digital video signals of the computer generally have to be converted into analog video signals for display on a traditional display device having an analog interface. The conventional KVM switch thus provides analog interfaces to transmit such video signals between computers and display devices. However, the analog video signals are easily affected by the transmission line, and the image constructed from the analog video signal is not good enough. On the other hand, a digital display working group (DDWG) established at the Intel Developer Forum (IDF) announced a new video interface, called the Digital Visual Interface (DVI), on September, 1998.
A main purpose of the DVI is to transmit video signals of a video display card directly to a display device, completely in digital format. The digital interface ensures that all video contents are transmitted in digital format to keep the data completeness of the whole transmission from the computer to the display device (without introduction of any interference signals), and thus a clearer and sharper image is obtained. Because the traditional and popular CRT display uses analog video signals, the conventional D-sub 15 pin connectors for displays are designed for the analog signals (complex signals). The digital video signals of the video display card have to be converted into analog video signals before being transmitted to the display when the conventional D-sub 15 pin connector is used. The conversions of digital/analog or analog/digital and the transmission of analog signals unavoidably degrade the image quality.
Digital displays including intrinsic digital designs, such as liquid crystal displays, liquid crystal projectors, plasma televisions, and liquid crystal television, have become popular and cheap in recent years. However, transmission of digital video signals through the conventional D-sub 15 pin connector, where the digital video signals are firstly converted into analog video signals for transmission to the digital display, and then are converted back into the digital video signals in the digital display, is both unwise and wasteful.